We have experienced our first extended stretch of warm and sunny weather in recent days on the heels of the coldest winter in decades. As is often the case at this time of year, however, we will revert back into a cool and unsettled pattern from late this week through early next week with frequent rounds of showers.

Quick April Recap

Winter did not give up easily this year as temperatures were 5ºF below average during the month of April. This marked the sixth consecutive month of below average temperatures, and of course this streak occurred during the six coldest months of the year.

Precipitation and snowfall ended up right around average during the month of April with 61 inches recorded at the Rendezvous Bowl Plot at 9,580 feet and 5 inches recorded in the Town of Jackson.

Season-to-date snowfall has reached 620 inches at the Rendezvous Bowl Plot, which is the third highest value as of May 1 over the past 15 years (the record is 649 inches in 2011 and 2017).

Season-to-date snowfall has reached 112 inches in the Town of Jackson, which is well above the seasonal average of 75 inches.

Recent Warm Temperatures

Following an exceptionally long and cold winter, the prolonged stretch of warm and sunny weather this week has been a welcome occurrence, even by some of the more hardcore powder hounds.

The warm-up began last Saturday as a ridge of high pressure took hold over the Intermountain West. After reaching a high of 69ºF in Jackson on Saturday, we are now (as of Wednesday) on day four in a row of 70ºF+ temperatures. The last time we hit 70ºF on four consecutive days was in early October.

This is actually a bit early to be seeing 70-degree weather as the average first 70ºF day in Jackson is May 5. The average high temperature at this time of year is around 60ºF.

Temperatures have generally been falling below freezing in the valley each morning, but shallow inversions have been in place with above-freezing overnight lows in the mountains. As a result, we have seen an increase in wet avalanche danger this week and the lack of overnight freezes have not been ideal for spring backcountry skiers.

Snowpack Update

Snowpack remains above average across the Upper Snake River Basin, which includes the Teton, Gros Ventre, and Snake River Ranges along with portions of the Wyoming Range and Southern Yellowstone. However, snowmelt has accelerated during the recent warm spell after peaking on April 26.

 

 

While it’s no secret that this has been a big winter in the Tetons, believe it or not, snowpack is only slightly above average in the Teton Range itself. This is surprising given the amount of snow that fell this season and the fact that temperatures were consistently below average for most of the winter.

The two snow telemetry stations (remote weather stations that measure snow water equivalent and snow depth) in the Tetons, the Grand Targhee Snotel and the Phillips Bench Snotel, are both 106% of average and 105% of average respectively as of May 3 in terms of the amount of water contained in the snowpack.

If we look at the depth of the snow on the ground, it’s a similar story at Jackson Hole Mountain Resort’s weather stations. Even though the Rendezvous Bowl Plot set a record for snowfall (the amount of snow that fell and accumulated, measured every 24 hours) this season, May 1 snow depth was only slightly above average compared to the previous 15 seasons.

 

 

The same is true at Jackson Hole’s Mid-Mountain Plot where May 1 snow depth was slightly above average.

 

 

So while we certainly have a healthy snowpack, higher elevation trails in the Tetons may only melt out slightly later than normal this summer, depending on late spring/early summer weather patterns. Snowpack percentages compared to average in surrounding mountain ranges and up into Yellowstone are a bit higher compared to the Tetons, however.

Also, late-season snow cover was among the deepest on record in parts of the Jackson Valley as of mid-April, and as a result, many of the lower elevation trails that begin to melt out in May will likely remain snowy and muddy later than usual.

Here is where we currently stand in terms of snow depth by location and elevation across the Tetons and up to Togwotee Pass.

 

 

Unsettled and Showery Weather Returns from Thursday Through Early Next Week

Wednesday will be the last sunny day with above-average warmth for a while. A slow-moving trough of low pressure located over the West Coast will work its way inland late this week, and a series of embedded disturbances will result in daily rounds of showers along with much cooler air.

Precipitation will generally be off-and-on and “showery” in nature with light to moderate amounts on any given day. Widespread long-duration precipitation events are unlikely.

The change in the pattern will begin on Thursday as a potent disturbance arrives from the south along with a cold front (oddly enough, the cold front will also be arriving from the south). An organized round of showers and thunderstorms is expected to develop during the midday to early afternoon hours on Thursday.

Highs will reach the 60s in the Jackson Hole Valley ahead of this system, then will fall into the 50s by later Thursday afternoon.

A relatively warm and unstable airmass will be in place as this disturbance approaches. As a result, we have a decent shot of seeing our first thunderstorm of the season around Jackson on Thursday. Cloud-to-ground lightning will be a possibility, so be alert if you have outdoor plans. Storm motions will be from south/southeast to north/northwest.

Snow levels will start out high, around 10,000 feet, during Thursday afternoon’s round. Another uptick in showers is possible late Thursday night as a second cold front moves through, with snow levels falling to 7,000-8,000 feet by Friday morning.

The pattern from Friday through Tuesday will feature off-and-on periods of showers along with cooler temperatures. Highs each day will range from the upper 40s to mid 50s in the valley with lows in the mid 30s.

Snow levels will generally range from 7,500-8,500 feet during the afternoon hours and 6,000-7,000 feet during the late night/early morning hours. So yes, we could see some flakes reach the lower valley floor during the morning hours from Saturday on, but accumulations are not expected.

Across the mid to higher elevations, light snow accumulations ranging from a trace to a couple of inches can be expected on any given day.

Total precipitation (rain and liquid-equivalent snow) over the next seven days should generally range from 0.75 to 1.5 inches in the Tetons and 0.5 to 1 inch in the valley. This is decent moisture but not exceptional for May, which on average is Jackson Hole’s rainiest month of the year.

More significant moisture is expected just west of our area across Idaho, as well as in the Cascade and Sierra Nevada Ranges.

 

 

Extended Outlook

During the second half of next week and beyond, confidence is low in how the pattern will play out. However, the latest trends indicate we may see a gradual transition into a warmer and drier pattern. That doesn’t mean we won’t see any rain (it is May after all), but shower activity may be less frequent compared to the previous week.

 

 

Alan Smith, Meteorologist

Alan is a professional meteorologist who holds a degree from MSU Denver and writes weather forecasts for Buckrail. He has lived in Jackson full-time since 2015. He is currently a Meteorologist and Operations Manager for OpenSnow, which is a weather forecasting service for skiing and outdoor adventures. At OpenSnow, Alan writes forecasts for the Tetons, Pacific Northwest, British Columbia, and North America as a whole.